Chile is preparing to launch its operation to rescue 33 miners trapped deep underground for more than three weeks.

Rescuers are expected on August 29 or 30 to start drilling an escape tunnel for the miners, who were trapped 700 meters down the gold and silver mine after a collapse on August 5.

Authorities estimate the operation will take up to four months.

The men appeared in good spirits in a self-made video, excerpts of which were broadcast on August 26 on national television.

But Health Minister Jaime Manalich, speaking to relatives camped out near the San Jose mine in Copiapo, said five miners were showing signs of depression.

"They're the most isolated, they don't want to appear on the screen, they're not feeding themselves well, to the extent that today we are going to act directly for these workers," Manalich said. "I would say depression is the right word."

Manalich said psychiatrists would attempt to treat the men via an intercom system sent down through a borehole.

Manalich said all the miners, who survived on small amounts of tinned tuna, milk, and cookies before being found alive on August 22, have lost a lot of weight and are still recovering from dehydration.

Keeping Spirits Up

Despite their ordeal, the men appeared generally healthy and in good spirits in the video, in which they are seen singing the national anthem and chanting "Long live Chile, long live the miners!"

One of the miners gives a tour of the shelter, showing where the men sleep, meet, play dominos, and pray. "We have everything organized," he says.

President Sebastian Pinera said on August 27 the government would do its best to help the miners cope with the agonizing wait.

Pinera said he had entrusted Manalich, on behalf of the government, to take charge of Operation San Lorenzo, who is the patron saint of miners.

"It consists of keeping them alive and in a sound physical and mental state during the months it is going to take for us to rescue them from the bowels of the earth," he said. "They will be provided with water, oxygen, food, medicine, and medical equipment for any emergency they may encounter."

Officials have promised to establish a permanent phone line next week so that the men can talk with their relatives.

Some who asked for cigarettes are getting nicotine gum. Letters from their families are lowered down as part of the effort to keep the miners' spirits up, and rescuers plan to send small projectors and entertainment equipment to help them fight boredom.

NASA Help

The government has also turned to NASA for advice on how to help the trapped cope with lengthy confinement.

"The Chileans are very well organized. They have a lot of resources at their disposal, they have done a lot for the miners," says Dr. Michael Duncan, deputy chief medical officer at the U.S. space agency.

"In fact, the miners have done a lot for themselves underground to show the will to survive and to organize themselves to be able to survive this long. So our plan is to go down and provide the advice that the Chileans have requested in the areas of nutritional support and behavioral health support."

The August 5 accident at the San Jose mine has underscored lax controls in mines.

Relatives of 28 of the miners are now suing the mine's owners, whom they blame for poor safety conditions that led to the cave-in.

A local judge has also preemptively frozen nearly $2 million of the mine's assets in case it has to pay compensation to the trapped miners' families.